An acoustic myography functional assessment of cerebral palsy subjects compared to healthy controls during physical exercise.

Individuals with cerebral palsy (CP) participate in reduced levels of physical activity and spend an increased amount of time in a sedentary state compared with healthy control subjects. Whether this in part can be explained by impaired muscle function is still unclear. The aim of the present study was to elucidate differences in muscle fibre recruitment during treadmill exercise between CP subjects and healthy age-, sex- and BMI-matched controls. This is a case-control study. Acoustic myography (AMG), a method recording fibre use and efficiency from contracting muscles, was applied during a period of treadmill exercise. The recorded AMG parameters revealed that the CP subjects had a significantly lower initial S-score (spatial summation) than the controls (P < 0.01). However, the T-score (temporal summation) and the E-score (efficiency) showed no significant differences between individuals with CP and the healthy control subjects. The present findings indicate that CP subjects use a higher degree of spatial summation (more fibres recruited) to keep up the same speed during treadmill exercise when compared to healthy matched control subjects. Our results suggest that individuals with CP have a tendency to recruit far more muscle fibres during bouts of exercise than healthy individuals. This may partly explain why CP subjects experience premature fatigue.

Microvascularization is not a limiting factor for exercise in adults with cerebral palsy.

Muscle contractures are a common complication in patients with central nervous system (CNS) lesions which limit range of movement and cause joint deformities. Furthermore, it has previously been shown that muscles with contractures have a reduced number of capillaries, indicating decreased tissue vascularization. The aim of the present study was to investigate the microvascular volume (MV) at rest and after acute exercise in the muscle tissue of individuals with cerebral palsy (CP) and healthy control individuals. Contrast-enhanced ultrasound (CEUS) was used before and after 30 min of walking or running on a treadmill in 10 healthy control participants and 10 individuals with CP to detect MV of their skeletal muscle tissue. A significant increase in the MV was observed after exercise both in the adult CP group (21-53 yr) and in the control group (21-52 yr) (1.8 ± 0.8 ΔdB to 3.1 ± 0.9 ΔdB or 42.9% and 1.5 ± 0.6 ΔdB to 2.5 ± 0.9 ΔdB or 39.0%, respectively). Furthermore, a difference in the resting MV was observed between the most severe cases of CP [gross motor function classification scale (GMFCS) 3 and 4] (2.3 ± 0.5 ΔdB) and the less severe cases (GMFCS 1 and 2) (1.5 ± 0.2 ΔdB). When the CP group was walking (3.4 km/h), the lactate levels, Borg score, and heart rate matched the level of controls when they were running (9.8 km/h). In conclusion, individuals with CP become exhausted at much lower exercise intensities than healthy individuals. This is not explained by impaired microvascularization, since the MV of the individuals with CP respond normally to increased O2 demand during acute exercise. NEW & NOTEWORTHY Cerebral palsy (CP) patients were less physically active compared with typically developed individuals. This may affect the microvascularization. We observed that the CP group became exhausted at much lower exercise intensities compared with healthy individuals. However, impaired microvascularization was not the reason for the decreased physical activity as the CP group responded normally to increased O2 demand during acute exercise. These results indicate that walking may be recommended as an intervention to train and maintain skeletal muscle tissue in individuals with CP.

Injection of high dose botulinum-toxin A leads to impaired skeletal muscle function and damage of the fibrilar and non-fibrilar structures.

Botulinum-toxin A (BoNT/A) is used for a wide range of conditions. Intramuscular administration of BoNT/A inhibits the release of acetylcholine at the neuromuscular junction from presynaptic motor neurons causing muscle-paralysis. The aim of the present study was to investigate the effect of high dose intramuscular BoNT/A injections (6 UI = 60 pg) on muscle tissue. The gait pattern of the rats was significantly affected 3 weeks after BoNT/A injection. The ankle joint rotated externally, the rats became flat footed, and the stride length decreased after BoNT/A injection. Additionally, there was clear evidence of microstructural changes on the tissue level by as evidenced by 3D imaging of the muscles by Synchrotron Radiation X-ray Tomographic Microscopy (SRXTM). Both the fibrillar and the non-fibrillar tissues were affected. The volume fraction of fibrillary tissue was reduced significantly and the non-fibrillar tissue increased. This was accompanied by a loss of the linear structure of the muscle tissue. Furthermore, gene expression analysis showed a significant upregulation of COL1A1, MMP-2, TGF-b1, IL-6, MHCIIA and MHCIIx in the BoNT/A injected leg, while MHVIIB was significantly downregulated. IN CONCLUSION: The present study reveals that high dose intramuscular BoNT/A injections cause microstructural damage of the muscle tissue, which contributes to impaired gait.